This invention relates generally to a laser welding method and apparatus for welding workpieces supported on a pallet transported by a conveyor system.
Laser welding systems that weld palletized assemblies transported by conveyor systems are known in the art. The conveyor systems index the palletized assemblies or workpieces into fixed positions to be welded.
A variety of approaches have been implemented for directing laser beams at various angles to the workpieces when they are presented in a position for welding. For example, U.S. Pat. Nos. 5,064,991 and 5,115,115 to Alborante; and U.S. Pat. No. 5,147,999 to Dekumbis et al.; disclose various methods for directing laser beams at workpieces. The Alborante ""991 patent discloses a plurality of laser emitter sets used in a vehicle framing station in which each set of emitters is designed to be used for the particular vehicle body style. Alborante ""115 patent discloses a laser torch on the end of a movable robot arm. Dekumbis et al. disclose a laser used for welding or coating a workpiece as well as means for manipulating a laser beam at various angles to the workpiece.
Existing laser welding systems also include a number of different approaches to controlling the movement of pallets and establishing the position of workpieces and pallets. For example, see U.S. Pat. No. 5,798,672 to Gilliland et al.; U.S. Pat. No. 6,018,136 to Ohmi et al.; U.S. Pat. No. 6,072,149 to Marmyama et al. Gilliland et al. disclose robot welding apparatus that includes a scanner that reads bar code labels and transmits positioning information to the robot or a welding apparatus controller. Ohmi et al. disclose a type of welding apparatus control system that includes a bar code scanner and reader for transmitting positioning information to a data processor that adjust the position of a welding torch. Maruyama et al disclose a laser welding apparatus for welding vehicle bodies. The apparatus includes a delivery system in which a beam path switching mirror can be moved in and out of the beam path to control the delivery of the beam to one or another scan head.
While they do not disclose laser welding per se, U.S. Pat. No. 6,072,419 to Maruyama et al. and U.S. Pat. No. 5,500,507 to Yoshiaki disclose manufacturing and machining systems respectively with systems for determining the positions of workpieces moving through an assembly line process. Watanabi U.S. Pat. No. 4,674,670 et al. disclose a manufacturing system for wire bonding lead frames in which the manufacturing process is automatically adjusted for the type of lead frame that is being bonded. The system includes TV cameras that view workpieces on a conveyor and provide positioning information, such as kind, shape and size of each workpiece to a central controller. The positioning information allows the controller to determine optimum wire bonding positions from each workpiece. Yoshiaki et al. disclose a laser beam machine system including a laser beam machine that can automatically machine a plurality of workpieces in sequence. A plurality of pallets, each supporting a workpiece, are stored in a pallet storing station or stoker, in a shelved manner. A transport device draws the pallet out from the pallet storing location and transports the pallet into the laser beam machine. After laser beam machining is completed, the pallet supporting the newly machined workpiece is stored in a predetermined location in the pallet storing station by the pallet transport device. The Yoshiaki et al. system also includes a memory medium disposed at a front surface of each pallet. Each memory medium stores information about the pallet that it is attached to. The information includes the type or configuration of workpiece supported on the pallet, the machining method to be used on the workpiece, and the storage position of the pallet within the stoker. A reader reads each memory medium and relays the information to a controller.
The invention is a laser welding apparatus for welding workpieces supported on a pallet transported by a conveyor system. The apparatus includes a laser generator and a laser manipulator configured and positioned to direct a laser beam emitted from the laser generator. The apparatus also includes a controller connected to the laser manipulator and configured to cause the laser manipulator to direct a laser beam from the laser generator at various predetermined angles toward predetermined positions within a laser work zone. A transport device is disposed adjacent the laser work zone and is configured to pass workpieces through the laser work zone where the laser beam manipulator can direct a laser beam onto desired interfacing portions of each workpiece to weld those interfacing portions together. The manipulator is additionally configured to weld the workpieces without halting workpiece motion through the laser work zone.
The invention also includes a method for welding work pieces supported on the pallet transported by a conveyor system. According to this method a laser manipulator is configured and positioned to receive a laser beam emitted from a laser generator. The laser manipulator is also configured and positioned to direct to that beam at various points within a laser work zone. A transport device is provided adjacent the laser work zone and is configured to pass work pieces through the laser work zone. A workpiece is then provided on a transport device and the transport device is caused to transport the workpiece through the laser work zone. Interfacing portions of the workpiece are then welded together by causing the laser beam manipulator to direct the laser beam at the interfacing portions as the workpiece is moving through the laser work zone.
According to another aspect of the invention, a pallet orientation sensor detects pallet orientation on the transport device and provides information to the controller that allows the controller to compensate for pallet orientation variations when commanding laser beam manipulator movement.
According to another aspect of the invention, the controller is programmed to direct the laser manipulator to weld pluralities of workpieces supported on single pallets disposed in a laser work zone. In a preferred embodiment, workpieces supported on a single pallet may be dissimilar from one another with the controller programmed to accomplish welds in selected interfacing regions of each dissimilar workpiece in the pallet in a single pass.
According to another aspect of the invention, the apparatus includes a two-way communication system. The communication system includes a pallet reader and a pallet programmer. The pallet reader is connected to the controller and sends signals to the controller corresponding to information read from passing pallets. The pallet programmer is also connected to the controller and uploads information to memory devices supported on the pallets. The pallet reader allows the controller to take into account information including pallet identification, the nature, quantity, orientation and position of workpieces supported on the pallet, processing history of workpieces on the pallet, the fixtures set-up holding the workpieces on the pallet, stage of assembly that the workpieces are in, and the destination in the origin of the pallet in the transport device. The pallet programmer allows information to be stored in individual pallets that can later be read by other pallet readers in the assembly line process. Information that the pallet programmer can upload to memory devices includes the type of process just completed on the workpiece supported on the pallet, the address of the station that the pallet should go to next for further processing, potential problems or flags detected by the controller such as workpieces out of position on the pallet, workpieces missing from the pallet, workpieces present on the pallet that the system does not recognize, and failure to complete a weld.
Objects, features and advantages of this invention include maximization of the use of laser welding machines by welding on the fly, the ability to weld parts almost continuously rather than waiting for parts to come to rest in a fixed position in a laser work zone, the ability to feed parts continuously into a welding apparatus while preceding parts are being welded, increasing the number workpiece surfaces that a laser can weld in a single pass because lines of sight between the manipulator and various workpieces are continuously changing as the workpieces pass through the laser work zone, and the ability to weld multiple workpieces supported on a single conveyor delivered pallet.